Electrical precipitators and energizing circuit therefor



ELECTRICAL PRECIPITATORS AND BNERGIZING CIRCUIT THEREFOR Filed Aug. 25,1954 Nov. 18, 1958 H. A. WINTERMUTE 4 Sheets-Sheet 1 I N VENTOR HARRYA.WINTERMUTE ATTORNEY Nov. 18, 1958 H. A. WINTERMUTE 2,860,723

ELECTRICAL PRECIPITATORS AND ENERGIZING CIRCUIT THEREFOR Filed Aug. 25,1954 4 Sheets-Sheet 2 "vvvvvv'hv nun lllllA 1 "1n n l INVENTOR 4M HARRYA.WINTERMUTE ATTORNEY Nov. 18, 1958 H. A. WINTERMUTE 2,860,723

ELECTRICAL PRECIPITATORS AND ENERGIZING CIRCUIT THEREFOR Filed Aug. 25,1954 4 Sheets-Sheet 3 INVENTOR HARRY A. WINTERMUTE BY ig/731M 'llllATTORNEY Nov. 18; 1958 H. A. WINTERMUTE ELECTRICAL PRECIPITATORS ANDENERGIZING CIRCUIT THEREFOR Filed Aug. 23. 1954 4 Sheets-Sheet 4 L I l'1 uncommon INVE "OR HARRY A. WINTERMUTE 1 BY WWW ATTORNEY United StatesPatent ELECTRICAL PRECIPITATORS AND'ENERGIZING CIRCUIT THEREFOR Harry A.Wintermute, Plainfield, N. 1., assignor to Research Corporation, NewYork, N. Y-., a corporation of New York Application.August-23, 1954,SerialNo. 451,397

14 Claims. (Cl. 183-7)- This invention relates to an arrangement forproducing and controlling respective high and low voltagessimultaneously from a single source for use. in electrical'precipitatorsand other electrical treating apparatus, such as emulsion breakingapparatus.

In modern electrical precipitators, there is often need for more than asingle treating voltage. This is particularly true of precipitatorshaving more than one treatment stage, or having different sections inwhich different electrode spacings or voltage requirements exist, or inwhich diilerent gas velocities may exist. Similarly, diiferent sectionsor locations in a precipitator may utilize different types ofelectrodes, requiring different voltages. Other considerations which mayrequire different voltages are different concentrations and types. ofdust particles suspended in the gas stream at different locations orsections, variations in gas conditions such as temperature,

water vapor content or other conditioning agents, and

differences-in the ionizing characteristics of the particular gas orgases being treated.

Different voltages for any of the above conditions can, of course, beobtained by using separatesources of energization for the differenttreating requirements, but this solution is obviously expensive, both ininitial cost and in the additional maintenance required. Voltage controlfor different voltage requirements can also be secured by usingresistance elements in, the high tension circuits. However, resistanceelements for this purpose are costly and less desirablev than theplacing of control means in the low tension circuits, since suchresistances are of very fine wire and require glazed surfaces to preventthe wires from quickly corroding through. Also,- on slight overloadsthese fine wires tend to burn out, necessitating shutdowns forreplacement of burned out elements. The necessity of meeting theresistance and/or ballasting requirements insueh an arrangement,together with the elimination of heat, makes this method of control alsorelatively expensrve.

It is a primary object of the invention to obviate the abovedifiiculties and disadvantages by securing voltage control for each ofthe half waves of the cycles of alternating current separately. Ingeneral, this is accomplished by the use of an electric valve orrectifier in the low tension circuit which passes current in only onedirection, and which is shunted by a resistance or other impedancedevice to pass a controlled amount of alternating current. The currentpassed by the rectifier and its shunt together supplies energy for onehalf wave, and that passed by. the shunt alone controls the value of theother half wave. Since the voltage for one of these half waves isgreater than for the-other, the voltage to one electrostatic sectionmaybe made greater than that for the other section by proper connectionon the high voltage side as will be shown below; The current flow'to'each of the. precipitator sections is dependent upon the operatingvoltage of that section. Alternatively, both half waves may beparalleled and connected to aprecipitator. unit, in which ice case theprecipitator is alternately energized with high and low voltages. Thishas the added advantage of reducing the peak voltage across therectifier unit without reducing the effective peak voltage across theprecipitator electrodes.

It is a particular advantage of the invention that the voltage controlelements are in all cases in the low tension or primary side of theprecipitator transformer.

The specific nature of the invention as well as other objects andadvantages thereof will clearly appear from a description of a preferredembodiment as shown in the accompanying drawing, in which:

Fig. 1 is a schematic circuit diagram of the invention as applied to asingle stage precipitator;

Fig. 2 is a schematic circuit diagram of the invention shown applied toa precipitator having two separate sections;

Fig. 3 shows another arrangement for supplying a two sectionprecipitator with different voltages;

Fig. 4 shows the invention applied to a precipitator having a highvoltage charging section and a low voltage precipitating section;

Fig. 5 shows the invention applied to a precipitator having a pluralityof sections, each having a different voltage;

Fig. 6 shows an alternative arrangement for supplying charging andprecipitator sections with different voltages;

Fig. 7 shows an arrangement similar to that of Fig. 2 with automaticcontrol added;

Fig. 8 shows the basic system of the invention, but.

using voltage regulating transformers in place of resistors; and

Fig. 9 shows an alternative arrangement for full Wave control accordingto the invention.

Referring to Fig. l, the precipitator conventionally represented at 1 issupplied with the usual high voltage transformer 2, suitably rectifiedby any conventional type of rectifier 3. Theprimary of transformer 2 issupplied with relatively low voltage from any suitable or conventionalsource through the customary ballasting'resistance 8 and is controlledor set to the desired operating value by means of voltage control 5.Voltage, control 5 comprises a half wave rectifier 9, which may be ofany known type, such as a kenetron tube or other electronic tuberectifier, copper oxide or selenium rectifier, etc., or may also be ahalf wave mechanical rectifier. In series with rectifier 9 is a variableresistor 7, and in-parallel with this series arrangement is a secondvariable resistor 6. Since the rectifier 9 passes current in-only onedirection, it will be apparent that the alternate half waves of currentflow in the opposite direction will be controlled entirely by thesetting of resistor-6. In the direction of current flow through therectifier, the current will be controlled by the value of resistor 6 inparallel with the com-- bined resistance of the rectifier 9 and variableresistor 7. In this manner, the-magnitude of current flow in bothdirections can be separately adjusted within reasonable limits, assufiicient for practical purposes. Thus each half cycle of current inthe primary circuit corresponding to current flow in one direction asindicated by the solid arrows can be controlled as to magnitude, whilethe half cycles of current in the opposite direction as indicated by thedotted arrows in the primary circuit can also be controlled as tomagnitude. In the secondary circuit, due to the orientation of rectifier3, current will flow only in the direction or the solid arrow. It willtherefore be seen that current flow through the resistor 6 (indicated bythe dotted arrow) will not directly contribute to theelectricaldischarge with the arrangement of Fig. 1. However, a distinctadvantage is derived from use of this arrangement in that it has beenfound that by its use the peak voltages across therectifier 9and'transformer 2 can be materially reduced without alfecting the peakoperating voltage across the precipitator. Without the resistor 6, andusing a conventional hookup, the peak voltages across the rectifier'andtransformer were found to be approximately thirty percent higher thanwhen the resistor is used, for the same precipitator voltage.

Fig. 2 shows the invention applied to a standard bridge valve typerectification hookup. In this case, two precipitator sections (or twoseparate precipitator units) 21a and 2112 are so connected in thetransformer secondary circuit that each is subject to current flow inone direction only. The direction of current flow in the circuit isrespectively indicated by solid and dotted arrows as before.

In Fig. 2 and in the succeeding figures, the same reference characterswill be employed as in Fig. 1, except that they will be preceded in thecase of Fig. 2 by a 2, in the case of Fig. 3 by a 3," etc. For example,rectifier 9 in Fig. 1 will be identified in Fig. 2 by numeral 29, inFig. 3 by 39, etc.

Continuing with Fig. 2, it will be apparent that the respective voltagesin precipitator section's 21a and 21b can be controlled by properlyadjusting resistors 26 and 27, as explained in connection with Fig. 1.In this way, by the use of a single control arrangement in the lowvoltage or primary side of the precipitator adjoining circuit, it ispossible to select two different operating voltages in the secondaryside for two different sections or parts of a precipitator, or' for twodifferent precipitators with all of the advantages previously mentioned.

It should be noted that precipitator sections 21a and 21b can also beoperated in parallel by simply electrically connecting together centeror discharge electrodes in the arrangement of Fig. 2, for example, bymeans of switch S With such an arrangement, successive half waves ofenergization of different amplitudes will be supplied to bothprecipitators together, and such a voltage supply may be desirable insome cases.

Fig. 3 shows an arrangement generally similar to Fig. 2, but using acenter tap transformer and half wave rectifier arrangement, aswill beapparent from inspection of the drawing. Here again, by connectingtogether the discharge electrode of the high voltage precipitator 31aand the low voltage precipitator 31b, parallel operation of theprecipitators with both receiving alternately high and low voltagepulses may be obtained.

Fig. 4 shows an arrangement generally similar to Fig. 3, except thatinstead of two similar precipitator sections, the invention is appliedto a precipitator having separate charging and precipitating sections,in which the precipitating section 4111, as is well known, generallyoperates at a much lower voltage than the charging section 41a. Thecontrol circuit of the present invention is well suited to this use, asit provide-s the necessary voltage in a single, simple and inexpensivearrangement, with all of the control elements in the low tension side.

Fig. shows an arrangement whereby three different voltages can beobtained in a precipitator by the use of the voltage control accordingto the invention. In this case, sections 5117 and 51b are respectivelysupplied with high and low voltage-s, as in the preceding arrangements.High voltage precipitator section 51a is supplied with the sum of thevoltages across 51b and 51b Condensers C and C serve as a voltagedividing reactance for supplying voltages to the respective sections,and also serve to smooth out the voltage fluctuations. If the voltagesacross C and C are respectively designated by X and X and the voltageacross precipitator section 51a is designated as X, then it will beapparent that voltage X equals X plus X While this arrangement does notpermit fully independent control of all three voltages, by proper designof the entire system, it will usually be possible to provide asatisfactory voltage relationship among all of the component parts.

It should be noted in connection with Fig. 5 that the rectifiers 53a and53b are so oriented that the charges on '4 these condensers arecumulative, thereby producing the desired voltage doubling effect.

Fig. 6 shows another arrangement for energizing charging andprecipitator sections from a common source of power with the chargingsection being energized at one voltage and the precipitating section ata lower voltage. The respective directions of the current flow areindicated as before by solid and dotted arrows, and the figure isself-explanatory.

Fig. 7 shows an arrangement generally similar to that of Fig. 2, butwith automatic voltage control added in combination with the respectivesections of the half wave control system, for controlling theenergization to give maximum or any desired operating conditions. Aseparate arcing control regulator 710, 711 and 712 is provided for eachprecipitator section and is indicated by the respective subscripts a andb. Each of these regulators may be of a known type, for example, such asthat shown in the following U. S. patents: Backer et al., 2,642,149;Willison, 2,666,496; Hall, 2,623,608 and 2,675,092. The high voltage iscontrolled by voltage regulator 713, and the low voltage by shuntresistance 76, each being controlled by its respective regulator. Theoperations of both sections are controlled by the arcing in therespective sections. During or after the high voltage setting is made,the low voltage control goes into operation and the voltage inthissection is brought to the desired point.

Fig. 8 shows an arrangement according to the invention using variabletransformer means 86 and 87 in place of the resistors 6 and 7 of thepreceding figures. The operation is essentially the same as in thepreceding figures, except that the rectifier 9 is noW shunted by awinding connected so as to buck the current flowing through the circuitdue to the line voltage. Alternatively, the winding 86a of transformer86 may be shunted across rectifier 89 alone, by means of switch Sinstead of across the combination of rectifier 89 and regulator 87. Theregulators may be either manually controlled or may be automaticallycontrolled in accordance with any known control system.

Fig. 9 shows an extension of the preceding arrangement in which theshunt regulator across the rectifier 99a is replaced by a second,oppositely oriented rectifier 9% which has in series with it its ownregulator 96. By the use of this symmetrical arrangement, it will beapparent that each half wave may be independently controlled. Thiscontrol arrangement may obviously be used with any of the precedingprecipitator arrangements, and give independent control of each sectionby means of a simple control arrangement in the low voltage side of theprecipitator charging circuit. Automatic voltage control equipmentsimilar to that shown in connection with Fig. 7 may be connected to boththe voltage regulators thereby regulating the voltages of eachprecipitator section independently of each other. In the place ofinductive regulators 96 and 97, any other suitable type of regulators,such as resistance regulators, may be employed.

It will be apparent that the embodiments shown are only exemplary andthat various modifications can be made in construction and arrangementwithin the scope of my invention as defined in the appended claims.

I claim:

1. A system for energizing electrical precipitators and the likeapparatus from a low voltage alternating current source comprisingstep-up transformer means supplied by said source, rectifying meansconnecting the electrodes of the apparatus to the secondary circuit ofsaid transformer means to provide unidirectional excitation for saidelec trodes, voltage control means in the primary circuit of. saidtransformer means comprising primary low im pedance diode rectifiermeans, and first impedance means shunting said primary rectifier meanswhereby respectively selective regulation of the half-waves ofcurrentfiowing in each direction is obtained.

2. The invention according to claim 1, including second impedance meansin series with said primary rectifier means, said first impedance meansshunting the series arrangement of said primary rectifier means and saidsecond impedance means.

3. The invention according to claim 2, said first impedance means beinga variable resistor.

4. The invention according to claim 3, said second impedance means beinga variable resistor.

5. A system for energizing electrical precipitators and the likeapparatus from a low voltage alternating current source comprisingvoltage step-up transformer means supplied by the source of low voltage,rectifying means connecting the electrodes of the electricalprecipitator apparatus to the secondary circuit of said transformermeans to provide unidirectional excitation for said electrodes, saidelectrodes comprise the respective electrodes of a first electricalprecipitation section and a second separate electrical precipitationsection, said rectifier means being arranged and oriented to supplyalternate half-waves of rectified voltage alternately to the electrodesof the respective precipitator sections, voltage control means in theprimary circuit of said transformer means comprising primary lowimpedance diode means, and first impedance means shunting said primaryrectifier means whereby respectively selective regulation of thehalf-waves of current flowing in each direction is obtained.

6. The invention according to claim 5 wherein an electrode of the firstprecipitator section is connected through a first rectifier to oneterminal of said transformer sec ondary, an electrode of the secondprecipitator section is connected through a second rectifier to theopposite terminal of said secondary, the other electrodes of the twosections being connected to a common junction point, said point beingconnected to said one terminal through a third rectifier oppositelyoriented from said first rectifier, and being also connected to saidopposite terminal through a fourth rectifier oppositely oriented fromsaid second rectifier, said first to fourth rectifiers comprising therectifying means of the secondary circuit.

7. The invention according to claim 5, wherein an electrode of the firstprecipitator section is connected through a first rectifier to oneterminal of said transformer secondary, an electrode of the secondprecipitator section is connected through a second rectifier to theopposite terminal of said secondary, the other electrodes of the twosections being connected to a common junction point, said common pointbeing connected to an intermediate point of said transformer secondary.

8. The invention according to claim 5, one of said sections being a highvoltage charging section and the other being a relatively low voltageprecipitating section.

9. The invention according to claim 2, the secondary rectifier meanscomprising a first rectifier connected to one secondary terminal and asecond rectifier connected in opposite orientation to the same terminal,a first condenser connected between said first rectifier and theopposite secondary terminal and a second condenser connected betweensaid second rectifier and said opposite terminal, a first electricalprecipitator section in parallel with said first condenser, a secondelectrical precipitator section in parallel with said second condenser,and a third electrical precipitator section connected across thenoncommon terminals of said condenser.

10. The invention according to claim 5, including a variable voltageregulator for controlling said low volt age alternating current source,and automatic voltage control means responsive to voltage conditions inone of said precipitator sections for controlling said variable voltageregulator.

11. The invention according to claim 10, including second automaticvoltage control means responsive to voltage conditions in the other ofsaid precipitator sections for adjusting said first impedance means.

12. The invention according to claim 2, said first impedance meanscomprising induction regulator means.

13. The invention according to claim 12, said second impedance meanscomprising second induction regulator means.

14. The invention according to claim 2, said first impedance meanscomprising the series arrangement of a second rectifier means oppositelyoriented to said first rectifier means and an induction regulator.

References Cited in the file of this patent UNITED STATES PATENTS1,935,460 Schmidt Nov. 14, 1933 2,010,600 Levy Aug. 6, 1935 2,126,790Logan Aug. 16, 1938 2,514,935 Clapp July 11, 1950 FOREIGN PATENTS528,815 Great Britain Nov. 7, 1940

